Diving as a lifestyle has evolved many times in the animal kingdom, and the ecology of all diving animals is essentially shaped by how long they can hold their breaths.
According to new research, the world’s diving animals – from small insects to giant whales – are all governed by a number of similar principles. Using the largest dataset ever compiled, an international team of scientists has examined how metabolic constraints govern the diving performance of air-breathing aquatic species, all of which have evolved to maximise the amount of time they can spend underwater.
They discovered that maximum dive duration increases predictably with body mass in all animals, but the rate at which this happens depends on metabolic mode.
Ectotherms – cold-blooded creatures such as amphibians, reptiles and insects – can remain submerged for longer at a given body mass, but the impact of an increase in body mass on dive duration in warm-blooded endotherms – including birds and mammals – is far more pronounced.
Writing in Proceedings of the Royal Society B, scientists say their findings constitute a new fundamental principle of evolutionary physiology, showing that the same ‘rules’ govern the evolution of diving in animals as different as water beetles and walruses.
They also say it may partly explain why many warm-blooded diving animals – including modern whales but also extinct reptiles such as ichthyosaurs and plesiosaurs – evolved relatively large body sizes, as increases in size led to greater relative increases in dive duration.